I have an array, for example:

var arr = [2,4,7,11,25,608,65,109,99,100,504,606,607];

I need to make it so each value that is within range of its multiple of ten below and and multiple of ten above it is grouped together.

For example, 2,4,7 are between 0 and 10 so they must be together. 11 would be alone in its group, like 25,65 etc. 606,607,608 would be together.

The array above should bee:

[ [2,4,7],[11],[25],[65],[99],[101],[504],[100,109],[606,607,608] ]

I've been thinking about it for a couple of hours and I wasn't able to e up with anything yet. It's really bad not much worth mentioning but so far I'm playing with Math.round (/)

Edit: I'd like to add another issue (although I will not pick the correct answer based on this if the actual answers don't include the solution of this new problem).

The array may contain values with letters. Those values should all be in the same group, in alphabetical order (only the first letter is taken to determine the order). This group should be the last value in the resulting array.

So for instance var arr = [2, 4, 11,'a3', 25, 7, 'j', 'bzy4];

Would be [[2,4,7],[11],[25],['a3','bzy4', 'j']]

I have an array, for example:

var arr = [2,4,7,11,25,608,65,109,99,100,504,606,607];

I need to make it so each value that is within range of its multiple of ten below and and multiple of ten above it is grouped together.

For example, 2,4,7 are between 0 and 10 so they must be together. 11 would be alone in its group, like 25,65 etc. 606,607,608 would be together.

The array above should bee:

[ [2,4,7],[11],[25],[65],[99],[101],[504],[100,109],[606,607,608] ]

I've been thinking about it for a couple of hours and I wasn't able to e up with anything yet. It's really bad not much worth mentioning but so far I'm playing with Math.round (http://jsfiddle/40napnyx/2/)

Edit: I'd like to add another issue (although I will not pick the correct answer based on this if the actual answers don't include the solution of this new problem).

The array may contain values with letters. Those values should all be in the same group, in alphabetical order (only the first letter is taken to determine the order). This group should be the last value in the resulting array.

So for instance var arr = [2, 4, 11,'a3', 25, 7, 'j', 'bzy4];

Would be [[2,4,7],[11],[25],['a3','bzy4', 'j']]

• javascript
• jquery
• arrays

• Where's your initial arr Array in the fiddle? what are you trying to do with math round? What about Numbers 10 and 100 ? – Roko C. Buljan Commented Feb 10, 2015 at 11:50
• in the fiddle, the for loop is as if the array contains numbers from 0-21. – Dan P. Commented Feb 10, 2015 at 11:52
• 2,4,7 are between 0 (the previous multiple of 10 of these numbers) and 10 (their next multiple of 10) so they should be grouped together. – Dan P. Commented Feb 10, 2015 at 11:53
• updated the fiddle to include the array of this example – Dan P. Commented Feb 10, 2015 at 11:56

2 Answers 2

Here's a generic function:

function groupBy(ary, keyFunc) {
  var r = {};
  ary.forEach(function(x) {
    var y = keyFunc(x);
    r[y] = (r[y] || []).concat(x);
  });
  return Object.keys(r).map(function(y) {
    return r[y];
  });
}

// usage:

var arr = [2,4,7,11,25,608,65,99,101,504,606,607];

g = groupBy(arr, function(x) { return Math.floor(x / 10) });

document.write(JSON.stringify(g));

For your bonus question, just apply groupBy twice:

    function groupBy(ary, keyFunc) {
      var r = {};
      ary.forEach(function(x) {
        var y = keyFunc(x);
        r[y] = (r[y] || []).concat(x);
      });
      return Object.keys(r).map(function(y) {
        return r[y];
      });
    }





var arr = [2, 4, 11,'a3', 25, 7, 'j', 'bzy4'];
g = groupBy(arr, isNaN);

g = [].concat(
  groupBy(g[0], function(x) { return Math.floor(x / 10) }),
  [g[1].sort()]
);
          
document.write(JSON.stringify(g));

This is what I came up with:

var arr = [2,4,7,11,25,65,99,101,504,606,607,608];
arr.sort(function(a, b) {
    if(a > b) return 1;
    if(a < b) return -1;
    else return 0;
});

var grouped_array = [];
for(var i = 0; i < arr.length; i++) {
    var group = [];
    var curr_group = Math.floor(arr[i]/10);
    while(Math.floor(arr[i]/10) == curr_group) {
        group.push(arr[i]);
        i++;
    }
    grouped_array.push(group);
}

http://jsfiddle/40napnyx/3/